lxd/util/config: Move unconditional break statement.
lxd/util/config: Move unconditional break statement.

The unconditional break may have caused config keys to be repeated
in the error message.

Signed-off-by: Mark Laing <e4eb1ed17d42befab1db63da5bbc17c0a2c16113@canonical.com>

stgraber/lxd,lxc/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,lxc/lxd,hallyn/lxd,lxc/lxd,stgraber/lxd